Environment & Energy
Related: About this forumAn Anthropogenic Iron "Invasion" of the Ocean Followed by Radioactive Polonium.
The paper I'll briefly discuss is this one: Anthropogenic Iron Invasion into the Ocean: Results from the East Sea (Japan Sea) Hojong Seo and Guebuem Kim Environmental Science & Technology 2023 57 (29), 10745-10753.
I am always interested in nuclear chemistry, and so this paper, which has nothing to do with the last best hope of humanity, nuclear power, but rather focuses on naturally occurring radioactive materials (NORM) and their use in tracing the source of iron in the oceans.
From the text:
The atmospheric depositional flux of anthropogenic Fe to the ocean has been mostly estimated by modeling approaches, although different results have been obtained depending on the study area and the model used. For instance, it was suggested that anthropogenic Fe contributed to the atmospheric supply of water-soluble Fe from 2 to 70% in the Northern Hemisphere. (24) In the Southern Ocean, the atmospheric depositional flux of anthropogenic Fe accounts for from insignificant proportions (less than 5%) to over half of the water-soluble Fe supply (>60%). (24?26) As such, global atmospheric models have shown approximately two orders of magnitude (0.130 Tg Fe yr1) differences in the water-soluble Fe flux (5,27) owing to the large uncertainties in obtaining the emission flux of Fe, the solubility of Fe for different sources and by atmospheric processes, and the lack of observational data for model validation. (28) In the real-world ocean, to our knowledge, Pinedo-González et al. (29) is the only study that provides in situ evidence of anthropogenic Fe contribution (2060%) to the dissolved Fe in the surface layer of the North Pacific Ocean using isotopic mass balance. However, the isotopic signature of Fe also has large uncertainties in quantifying anthropogenic Fe in the ocean because of isotopic fractionation associated with biological production, scavenging, and ligand complexation. (30)
Thus, in this study, we used various tracers (Al, K, V, Ni, Pb, and 210Pb) to identify the main sources of anthropogenic Fe in 72 aerosol samples collected over one year in the eastern coastal region of Korea, located in the northwestern Pacific Ocean (Figure 1). In addition, we used 210Pb as a tracer of the atmospheric fallout flux of anthropogenic Fe. Furthermore, we evaluated the contribution of anthropogenic Fe to seawater based on a non-steady-state scavenging model, including the 210Pb-derived Fe flux and the measured Fe concentrations in the East Sea (Japan Sea). Since this sea is located in the downwind of Asian aerosol sources and is almost fully closed from 200 to 3000 m, the results in this region may reveal what is happening in the global ocean with the invasion of anthropogenic Fe...
The use of Pb-210 - measured as its daughter Po-210 (polonium) from the natural decay series of U-238 is rationalized thus:
The measurement technique is interesting:
Some pictures from the text:
The caption:
The caption:
Figure 3. Sources of anthropogenic Fe and its relationship with 210Pb in aerosols. (a) Plot between non-sea-salt potassium-to-aluminum ratios (nss-K/Al) and non-sea-salt vanadium-to-aluminum ratios (nss-V/Al). The error bars for each end-member represent a 1-standard deviation from average values. The color gradient indicates Fe solubility. (b) Anthropogenic Fe in water-soluble fraction versus excess 210Pb. The dashed line represents the slope and intercept of a linear regression of data (r = 0.66 and p < 0.001). The error bars for excess 210Pb are based on 1-standard deviation counting statistics.
The caption:
I'm not sure I entirely buy into the method; I'd need to think about it more, which is not to say that I know it doesn't work.
It's an interesting idea however, worth thinking about.
Enjoy Friday.
John ONeill
(60 posts)If humans are already unintentionally putting significant amounts of biologically available iron into the ocean, that is presumably helping to counteract some of the carbon dioxide we're also unintentionally putting in the biosphere. Increased marine iron levels during ice ages, caused by glacial 'flour' blowing off arid river deltas, and directly from meltwater runoff, were a positive feedback, from diatoms sequestering carbon and further reducing temperatures. Putting more Fe into areas of the oceans where lack of it inhibits plankton growth would seem like a sensible move, except to the likes of the World Wildlife Fund and Greenpeace. Our decimation of whale populations probably led to abnormally low levels of iron, as whale faeces are supposed to pump the element up from the deep ocean. Till whale populations recover, and we can wean our economy off fossil fuels, any way of lowering atmospheric CO2 (and ocean acidity) should at least be studied.
The same applies to sulfate aerosols, which until recently were believed to be counteracting up to a third of the warming effect of GHGs. Recent steep rises in temperatures may be associated with the world agreement on phasing out bunker fuels for ships. Though no fun for inhabitants of ports they frequented, the ships left cloud wakes visible from satellites, with much lower albedo than the ocean either side of them. As Stewart Brand says, 'We are as gods, and have to get good at it.'